Polarizer protective film, polarizing plate and liquid crystal display device

Abstract

To provide a polarizer protective film, a polarizing plate, and a liquid crystal display device with which it is possible to suppress the warp of a liquid crystal panel.SOLUTION: Provided is a polyester film for polarizer protection that is laminated on one plane of a polarizer, the polyester film for polarizer protection satisfying the requirements (1) and (2) below. (1) The contractive force Ff of the polyester film in a direction parallel to the transmission axis of the polarizer is 800 N / m to 9000 N / m inclusive; (2) The ratio (Ff / Fv) of the contractive force Ff of the polyester film in a direction parallel to the transmission axis of the polarizer to the contractive force Fv of the polyester film in a direction parallel to the absorption axis of the polarizer is 2.5 to 12.0 inclusive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polarizer protective film, a polarizing plate, and a liquid crystal display device. [Background technology]

[0002] Demand for LCD devices is expanding for applications such as LCD televisions and PC displays. Generally, a liquid crystal display device consists of a transparent electrode, a liquid crystal layer, a color filter, etc. sandwiched between glass plates. It consists of a liquid crystal cell embedded in it and two polarizing plates on either side of it. A polarizing plate is a polarizer (also called a polarizing film) sandwiched between two optical films (for example, a polarizer protection film). The structure is sandwiched between a glass substrate (a glass substrate and a retardation film).

[0003] In recent years, LCD TV screens have become thinner and larger, and LED backlights are being used as light sources. As a result, the thickness of the glass substrate used in LCD panels became less than 0.7 mm. As the display became thinner, problems arose with uneven display, and improvements were required. are. The mechanism by which display unevenness occurs is mainly due to the shrinkage of the polarizer. When placed in a high temperature and humidity environment, a shrinkage force acts in the direction of the orientation in order to relax the orientation. As a result, the LCD panel warps and bulges toward the backlight unit, causing uneven display. It is believed that...

[0004] Conventionally, as in Patent Documents 1 and 2 below, glass used in liquid crystal panels has The thickness of the glass substrate was 0.7 mm or more, so the high rigidity of the glass prevented the polarizer from shrinking. This minimizes the risk of the LCD panel warping, and uneven display was not an issue.

[0005] Therefore, we have developed a method to prevent the warping of LCD panels that occurs when glass substrates are made thinner than 0.7 mm. Attempts are being made to improve this with academic films. For example, when a cycloolefin resin is used as a polarizer protective film, the liquid crystal panel The improvement of the warp of the flannel was insufficient, and the drying time of the water glue used to attach the polarizer was poor. This resulted in a problem of reduced productivity. In addition, conventional triacetyl cellulose (TAC) is used as the polarizer protective film. If this is done, there is a problem of the LCD panel warping. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-107499 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-198666 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to and a polarizer protective film, a polarizing plate, and a liquid crystal display device that can suppress warping. That is the thing. [Means for solving the problem]

[0008] In order to solve the above problem, the inventors have been investigating the causes of the above problem. , the shrinkage force of the polyester film for protecting the polarizer in the direction parallel to the transmission axis of the polarizer It was discovered that the warpage of liquid crystal panels can be improved by setting the thickness within a specific range. Based on this finding, the present invention was achieved.

[0009] In detail, a liquid crystal display device usually has a polarizer on one side of a liquid crystal cell, the transmission axis of which is aligned with the liquid crystal. The polarizing plate is laminated so that it is parallel to the long side of the display device, and the polarizer absorption The polarizing plates are stacked so that their axial direction is parallel to the long sides of the LCD device. As a result of careful investigation using a display device, it was found that the absorption axis direction of the polarizer with the largest shrinkage force is the long side. The problem is the shape factor, which makes the polarizing plate more likely to curl due to shrinkage (curl is generally This is due to the influence of the asymmetrical configuration of the upper and lower polarizers in the LCD panel. The liquid crystal panel is a polarized panel in which the polarizer transmission axis of the upper and lower polarizing plates arranged in a crossed Nicol configuration is the long side. The present inventors have found that the problem lies in the fact that the light source is convex toward the light plate side.

[0010] Furthermore, as a result of careful investigation, the contraction force in the long side direction of the polarizing plate, in which the polarizer transmission axis is the long side, is It was revealed that the shrinkage force can be controlled by the residual strain of the protective film. It was found that curling of the LCD panel can be controlled.

[0011] Here, a method for measuring the shrinkage force of the polyester film for protecting a polarizer will be described. Generally, the shrinkage force of a film is measured using a TMA or similar device at the start of the test at a low temperature with a very small load. The initial length is set, and the force in the contraction direction is measured while the temperature is rising while maintaining the initial length. However, during the temperature rise process, shrinkage ( At the same time, the free volume and occupied volume of the polymer decrease due to the temperature rise. Since the increase in temperature causes thermal expansion (hereinafter simply referred to as thermal expansion), polyester In the temperature range around the glass transition temperature of the film (for example, about Tg + 50°C), Since the relationship between thermal contraction and thermal expansion is often true, the film as a whole expands and the shrinkage force is not observed. I can't.

[0012] As a result of the investigation, even if no contraction force occurs during the TMA heating process, It was revealed that a contraction force occurs. This is because the strain caused by thermal expansion is a reversible change. After heating and cooling, the material returns to its original state, but when cooled, it is in a smaller size due to the amount of thermal contraction that occurred during the heating process. This is because thermal stress occurs during the cooling process. The shrinkage force after cooling can be expressed by the following formula. The heat shrinkage rate in the present invention includes the change in moisture content during heat treatment. Contraction force (N / m) = Film thickness (mm) × Elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) ÷ 100 x 1000

[0013] That is, the representative aspects of the present invention are as follows. Section 1. A polyester film for protecting a polarizer that is laminated on one surface of a polarizer and that meets the following requirements: A polyester film for protecting polarizers that satisfies requirements (1) and (2). (1) The shrinkage force F of the polyester film in the direction parallel to the transmission axis of the polarizer f but 800N / m or more and 9000N / m or less (however, the contraction force F f (N / m) is the Thickness of sterilized film (mm) x Elastic modulus (N / mm 2 ) × 80℃ 30 minutes heat shrinkage rate (%)÷100×1000. Here, the elastic modulus is the modulus in the direction parallel to the transmission axis of the polarizer. The heat shrinkage is the elastic modulus of the polyester film in the direction parallel to the transmission axis of the polarizer. (The heat shrinkage rate of the polyester film at (2) The shrinkage force F of the polyester film in the direction parallel to the transmission axis of the polarizer f and The shrinkage force F of the polyester film in the direction parallel to the absorption axis of the polarizer v Ratio of (F f / F v ) is 2.5 or more and 12.0 or less (however, the contractile force F v (N / m) is the Thickness of sterilized film (mm) x Elastic modulus (N / mm 2 ) × 80℃ 30 minutes heat shrinkage rate (%) ÷ 100 × 1000. Here, the elastic modulus is the modulus in the direction parallel to the absorption axis of the polarizer. The heat shrinkage is the elastic modulus of the polyester film in the direction parallel to the absorption axis of the polarizer. (The heat shrinkage rate of the polyester film at Section 2. Item 1. The polyester film for protecting a polarizer according to Item 1, further satisfying the following requirement (3): (3) The direction in which the heat shrinkage rate of the polyester film is maximum is parallel to the transmission axis of the polarizer. The directions are almost parallel Section 3. Item 1, wherein the polyester film has a retardation of 3,000 to 30,000 nm. 3. The polyester film for protecting a polarizer according to claim 2. Section 4. Items 1 to 3, characterized in that the thickness of the polyester film is 40 to 200 μm. 10. The polyester film for protecting a polarizer according to claim 9, Section 5. A hard coat is applied to the surface of the polyester film opposite to the surface on which the polarizer is laminated. Any of items 1 to 4, having a layer, an antireflection layer, a low reflection layer, an antiglare layer, or an antireflection and antiglare layer. The polyester film for protecting a polarizer according to any one of the preceding claims. Section 6. A polyester film for protecting a polarizer that is laminated on one surface of a polarizer and that meets the following requirements: A polyester film for protecting polarizers that satisfies requirements (1) and (2). (1) The TD shrinkage force F of the polyester film TD is 800N / m or more, 9000N / m or less (however, the contractile force F TD (N / m) is the thickness of the polyester film (mm ) × Elasticity (N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80℃ ÷ 100 × 1000 Here, the elastic modulus is the TD elastic modulus of the polyester film, and the heat shrinkage is the (The thermal shrinkage rate of polyester film in TD.) (2) The TD shrinkage force F of the polyester film TD and M of the polyester film Contraction force F of D MD Ratio of (F TD / F MD ) is between 2.5 and 12.0 (however, Contraction force F MD (N / m) is the thickness of the polyester film (mm) x the elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80°C ÷ 100 × 1000. Here, the elastic modulus is The MD elastic modulus of the polyester film, and the heat shrinkage rate is the MD elastic modulus of the polyester film. is the thermal shrinkage rate.) Section 7. Item 7. The polyester film for protecting a polarizer according to item 6, further satisfying the following requirement (3): (3) The direction in which the heat shrinkage rate of the polyester film is maximum is approximately parallel to the TD. Section 8. Item 8. The polyester for protecting a polarizer according to any one of Items 1 to 7, A polarizing plate made by laminating films. Section 9. The polyester film for protecting a polarizer according to any one of items 1 to 7 is provided on one surface of the polarizer. A polarizing plate that is laminated and has no film on the other side of the polarizer. Section 10. The polarizing plate has a rectangular shape, and the long side of the polarizing plate and its transmission axis are parallel to each other. The polarizing plate according to claim 1. Section 11. A liquid crystal display device having a backlight source and a liquid crystal cell disposed between two polarizing plates. At least one of the two polarizing plates is the polarizing plate according to any one of items 8 to 10. That is, a liquid crystal display device. [Effects of the Invention]

[0014] According to the present invention, a polarizer protective film capable of suppressing warpage of a liquid crystal panel, a polarizing A liquid crystal display device and a display panel can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0015] The polyester film for protecting a polarizer of the present invention is made of a polyester film and At least one surface of the film (for example, a film made of polyvinyl alcohol and a pigment) is laminated. It is a polarizer protective film that is layered to form a polarizing plate.

[0016] In this specification, the convergence of the polyester film in the direction parallel to the transmission axis of the polarizer The contraction force is the force of the polyester film in the direction parallel to the transmission axis of the polarizer laminated on one side of the polyester film. This refers to the shrinkage force of polyester film. The heat shrinkage of the polyester film in the direction parallel to the transmission axis of the polarizer is The polyester film is laminated on one side of the steric film in a direction parallel to the transmission axis of the polarizer. This refers to the thermal shrinkage rate of the material. The elastic modulus of the polyester film in the direction parallel to the transmission axis of the polarizer is A polyester film is laminated on one side of the polarizer in a direction parallel to the transmission axis of the polarizer. This means the modulus of elasticity. The shrinkage force of the polyester film in the direction parallel to the absorption axis of the polarizer is The direction of the absorption axis of the polyester film is parallel to the direction of the absorption axis of the polarizer laminated on one side of the polyester film. This refers to the contractile force of the film. The heat shrinkage of the polyester film in the direction parallel to the absorption axis of the polarizer is The polyester film is laminated on one side of the steric film in a direction parallel to the absorption axis of the polarizer. This refers to the thermal shrinkage rate of the material. The elastic modulus of the polyester film in the direction parallel to the absorption axis of the polarizer is A polyester film is laminated on one side of the polarizer in a direction parallel to the absorption axis of the polarizer. This means the modulus of elasticity. The direction parallel to the transmission axis of the polarizer is sometimes simply called the transmission axis direction of the polarizer. In addition, the direction parallel to the absorption axis of the polarizer may be simply referred to as the absorption axis direction of the polarizer.

[0017] The polyester film for protecting a polarizer of the present invention has a direction parallel to the transmission axis of the polarizer and a direction parallel to the transmission axis of the polarizer. It is preferable that the directions in which the heat shrinkage rate of the steril film is maximum are in a substantially parallel relationship. The direction of the transmission axis of the polarizer and the direction in which the heat shrinkage rate of the polyester film is maximum is called the direction of the transmission axis of the polarizer and the direction in which the heat shrinkage rate of the polyester film is maximum. The absolute value of the angle between the The gradient of the heat shrinkage rate is preferably 12 degrees or less, and more preferably Preferably, the angle is 10 degrees or less, more preferably 8 degrees or less, and even more preferably 6 degrees or less. The thermal shrinkage is preferably 4 degrees or less, and more preferably 2 degrees or less. The smaller the inclination, the better, so the lower limit is 0 degrees. Heat shrinkage rate of polyester film If the tilt is large, the polarizing plate containing the polyester film will warp in the diagonal direction, causing the LCD panel to However, the effect of reducing warping of the flannel tends to be reduced. However, the shrinkage force F of the polyester film in the direction parallel to the transmission axis of the polarizer f and The contraction force F of the polyester film in the direction parallel to the photon absorption axis v Ratio of (F f / F v ) is 2.5 or more and 12.0 or less, the direction parallel to the transmission axis of the polarizer and the direction parallel to the polyester film Even if the absolute value of the angle between the direction where the film's thermal shrinkage rate is maximum is 40 degrees or less, The angle is preferably 35 degrees or less. Heat shrinkage rate of polyester film, slope of heat shrinkage rate of polyester film, and The direction in which the heat shrinkage rate of the polyester film is maximum is measured by the method employed in the examples described later. It can be determined.

[0018] Normally, in a liquid crystal display device, two polarizing plates are arranged in a crossed Nicol relationship. When two polarizing plates are arranged in a crossed Nicol relationship, light normally passes through the two polarizing plates. However, the shrinkage or warping of the polarizer as mentioned above results in a complete cross-polarization. In order to prevent light leakage, the polarizer The direction in which the thermal shrinkage of the protective film is greatest and the angle between the polarizer's transmission axis is smaller is preferred.

[0019] The polyester film for protecting a polarizer of the present invention has a polarizing effect in a direction parallel to the transmission axis of the polarizer. The shrinkage force Ff of the polyester film is 800N / m or more and 9000N / m or less. It is desirable. F fIf the lower limit is less than 800 N / m, the warpage of the liquid crystal panel is not sufficiently reduced. In addition, F f If the upper limit of 9000N / m is exceeded, shrinkage If the force is too strong, the LCD panel may bend in the opposite direction. is 900N / m or more and 8000N / m or less, and more preferably 1000N / m or more and 80 1000N / m or less, and more preferably 1100N / m or more and 8000N / m or less. More preferably, it is 1200 N / m or more and 8000 N / m or less. It is preferable that the strength is 000N / m or less, 5500N / m or less, or 4800N / m or less.

[0020] Here, the contractile force F f is the polarization of the polyester film in the direction parallel to the transmission axis of the polarizer The shrinkage force is calculated by multiplying the thickness of the polyester film (mm) by the modulus of elasticity (N / mm 2 )×80℃ Defined as the heat shrinkage rate (%) after 30 minutes of treatment ÷ 100 × 1000. Here, the elastic modulus is the elastic modulus of the polyester film in the direction parallel to the transmission axis of the polarizer. The heat shrinkage rate is the rate of shrinkage of polyester in the direction parallel to the transmission axis of the polarizer. This refers to the heat shrinkage rate of terephthalate film (heat shrinkage rate when heated at 80°C for 30 minutes).

[0021] The shrinkage force of the polyester film in the direction parallel to the absorption axis of the polarizer is F v Let's say. Contraction force F v is the thickness of the polyester film (mm) x modulus of elasticity (N / mm 2 )×80℃ It is defined as the heat shrinkage rate (%) after 30 minutes of treatment ÷ 100 × 1000. Here, the elastic modulus is the This is the elastic modulus of the polyester film in the direction parallel to the absorption axis of the film. The heat shrinkage rate of the polyester film in the direction parallel to the absorption axis of the polarizer (at 80°C -Thermal shrinkage rate after 30 minutes of heat treatment.

[0022] The polyester film for protecting a polarizer of the present invention is F f / F v is between 1.0 and 12.0 It is more preferable that the ratio is 2.5 or more and 12.0 or less. f / F v Under If the limit is less than 1.0, warpage of the liquid crystal panel may not be reduced sufficiently. Also, F f / F v If the upper limit of 12.0 is exceeded, the thermal deformation in one direction increases, and the polarization The protective film is laminated on the side opposite to the side on which the polarizer protective polyester film is laminated. This may cause stress to the film and retardation film, which may result in a deterioration in display quality. This may result in a decrease in stability and lead to breakage.

[0023] As a method for controlling the shrinkage force within the range of the above formula, the heat treatment step after film stretching is completed. and then stretching the film again while controlling the winding tension. .

[0024] The polyester film for protecting a polarizer of the present invention has a thickness of 100 μm to 120 μm. Elastic modulus of sterilized film: 1000~9000N / mm 2 It is preferable that the The shrinkage force of the steric film can be controlled by the elastic modulus, but the shrinkage force of the polyester film in the direction of the transmission axis of the polarizer In order to increase the elastic modulus of the polyester film, the polyester film is It is necessary to highly orient the polarizer and increase the crystallinity. The elastic modulus of polyester film is 9000N / mm 2 If it exceeds this limit, it may become easily torn. Therefore, the upper limit is 9000N / mm 2 is preferred, and more preferably 80 00N / mm 2 and more preferably 7000 N / mm 2 is. On the other hand, if the orientation is low and the crystallinity is low, thickness unevenness occurs when the film is wound on a roll. The unevenness of the roll caused by this may cause deformation of the film, resulting in poor flatness. The lower limit of the elastic modulus is 1000N / mm 2 is preferable, and more preferably 1500 N / mm 2 and more preferably 1800 N / mm 2 The modulus of elasticity is the same as that used in the examples described below. It can be measured in this way.

[0025] The polyester film for protecting a polarizer of the present invention has a thickness of 100 μm to 120 μm. The heat shrinkage rate of sterilized film when heated at 80℃ for 30 minutes is 0.10 to 5.0%. The lower limit of the heat shrinkage rate is preferably 0.10% or more, and more preferably 0.15% or more. The upper limit of the thermal shrinkage is preferably 4.5% or less, and most preferably 0.20% or more. 0% or less is more preferable, 3.0% or less is even more preferable, and 2% or less is even more preferable. The most preferable value is 1.4% or less. If the thermal shrinkage rate is lower than 0.10%, that is, 0.0 In the range of 1 to 0.099%, it is difficult to control the thermal shrinkage rate evenly. In addition, in order to increase the heat shrinkage rate above 5.0%, it is necessary to further increase the crystallinity and glass transition temperature. It is necessary to further reduce the thickness, which may result in problems such as poor flatness. The heat shrinkage rate can be measured by the method employed in the examples described below.

[0026] The polyester film for protecting a polarizer of the present invention has a thickness of 40 to 200 μm. It is preferably 40 to 100 μm, more preferably 40 to 80 μm. If the thickness of the polyester film is less than 40 μm, it will be easily cracked and will lack rigidity. In addition, when the film is thin, the transmittance of the polarizer is accordingly reduced. It is necessary to increase the modulus of elasticity or heat shrinkage of the polyester film in the transaxial direction. As mentioned above, each parameter has an upper limit, so 40 μm is the practical lower limit. In addition, when the thickness of the film exceeds 200 μm, the direction of the transmission axis of the polarizer is changed accordingly. The variation in the elastic modulus or heat shrinkage rate of the polyester film increases, and it is difficult to control this. This may make it difficult to apply the polyester film, and also increases costs. It can be measured by the method employed in the examples described below.

[0027] The polyester film for protecting a polarizer of the present invention is effective in preventing rainbows from being observed on the screen of a liquid crystal display device. From the viewpoint of suppressing unevenness, it is preferable that the in-plane retardation is within a specific range. The lower limit of the dation is 3000nm or more, 5000nm or more, 6000nm or more, 700 The upper limit of the in-plane retardation is preferably 0 nm or more, or 8000 nm or more. , 30,000 nm or less is preferable, more preferably 18,000 nm or less, and even more preferably In particular, from the viewpoint of thinning, the in-plane retardation is 100 Preferably, it is less than 000 nm, and 9000 nm or less.

[0028] The retardation of polyester film is determined by measuring the refractive index in two directions and the thickness. It is also possible to use commercially available automatic instruments such as the KOBRA-21ADH (Oji Instruments Co., Ltd.). The refractive index can also be determined using a birefringence measuring device. It can be determined by measuring the wavelength (589 nm).

[0029] The polyester film for protecting a polarizer of the present invention has an in-plane retardation (Re) and a thickness direction The ratio (Re / Rth) of the retardation in the direction of the polarization (Rth) is preferably 0.2 or more. or 0.3 or more, preferably 0.4 or more, more preferably 0.5 or more, and even more preferably The ratio of the in-plane retardation to the thickness retardation (Re / R The larger th), the more isotropic the birefringence becomes, and the less rainbow-like color spots appear depending on the observation angle. In a completely uniaxial (symmetrical) film, the above retardation and The thickness retardation ratio (Re / Rth) is 2.0, so the above retardation The upper limit of the ratio of retardation to thickness direction retardation (Re / Rth) is preferably 2.0. The upper limit of Re / Rth is 1.2. When viewed from the cross section in the direction, the two birefringences △Nxz and △Nyz are multiplied by the film thickness d. This means the average phase difference obtained by

[0030] In order to further suppress rainbow-like color spots, the polyester film for protecting a polarizer of the present invention has the following features: The NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2. It is preferably 0.0 or less, more preferably 1.8 or less, and even more preferably 1.6 or less. Therefore, the NZ coefficient is 1.0 for a perfect uniaxial (symmetric) film, so the NZ coefficient is The limit is 1.0. However, as we approach a completely uniaxial (symmetrical) film, the orientation direction It should be noted that the mechanical strength in the direction perpendicular to the direction of the bending moment tends to decrease significantly.

[0031] The NZ coefficient is expressed as |Ny-Nz| / |Ny-Nx|, where Ny is the polyester fiber. Nx is the refractive index in the direction perpendicular to the slow axis of the film (refractive index in the direction of the fast axis) Nz represents the refractive index in the thickness direction. The orientation axis of the film was determined using a molecular orientation meter (004 type), and the orientation axis and the direction perpendicular to it were measured. The biaxial refractive index in the direction (Ny, Nx, where Ny>Nx) and the refractive index in the thickness direction (Nz) are The refractive index is measured using a Refractometer (NAR-4T, manufactured by Atago Co., Ltd., measuring wavelength 589 nm). The value thus obtained can be substituted into |Ny-Nz| / |Ny-Nx| to obtain the NZ coefficient. This can be done.

[0032] In addition, in order to further suppress rainbow-like color spots, the polyester film of the present invention is The Ny-Nx value of the steric film is preferably 0.05 or more, more preferably 0.07 or more, more preferably 0.08 or more, even more preferably 0.09 or more, and most preferably The upper limit is not specified, but polyethylene terephthalate films In this case, the upper limit is preferably about 1.5.

[0033] The polyester film of the present invention can be obtained from any polyester resin. The type of polyester resin is not particularly limited, and may be any resin obtained by condensing a dicarboxylic acid and a diol. Any polyester resin suitable for use in the present invention may be used.

[0034] Dicarboxylic acid components that can be used in the production of polyester resins include, for example, terephthalic acid. Acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid Dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid , diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarbo anthracene dicarboxylic acid, 1,3-cyclopentane dicarboxylic acid, 1,3-cyclopentane dicarboxylic acid 1,4-Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-di Ethyl succinic acid, glutaric acid, 2,2-dimethyl glutaric acid, adipic acid, 2-methyl adipic acid Dipic acid, trimethyl adipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid , suberic acid, dodecadicarboxylic acid, etc.

[0035] Examples of diol components that can be used in the production of polyester resins include ethylene glycol diols. ethanol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1 ,2-Cyclohexanedimethanol, 1,4-Cyclohexanedimethanol, decamethylene Glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentane Diol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane , bis(4-hydroxyphenyl)sulfone, and the like.

[0036] The dicarboxylic acid component and the diol component constituting the polyester resin are each one or two kinds. Suitable polyester resins for the polyester film include: Examples of the polyester include polyethylene terephthalate, polypropylene terephthalate, and poly butylene terephthalate, polyethylene naphthalate, etc., and more preferably polyethylene Examples of such a compound include polyethylene terephthalate and polyethylene naphthalate. These resins have excellent transparency and are thermally and mechanically stable. It also has excellent mechanical properties. In particular, polyethylene terephthalate can achieve a high elastic modulus. Furthermore, it is a suitable material because the heat shrinkage rate can be controlled relatively easily.

[0037] When it is necessary to highly increase the heat shrinkage rate of polyester film, a copolymer component is added. It is desirable to add a temperature to reduce the degree of crystallinity appropriately. Since the rate of elastic deformation and permanent deformation is high, it is generally Therefore, it is preferable to incorporate a component with a low glass transition temperature as needed. Specifically, propylene glycol, 1,3-propanediol, etc. is.

[0038] (Adding a functional layer) The polarizing plate using the polyester film for protecting a polarizer of the present invention is It is desirable that the film be integrated with the glass plate of the liquid crystal cell while the thermal shrinkage rate of Easy-adhesion layer, hard coat layer, anti-glare layer, anti-reflection layer, low-reflection layer, low-reflection layer, anti-reflection layer When functional layers such as a glare layer, a low reflection anti-glare layer, and an antistatic layer are added, the drying temperature should be lowered. It is desirable to set the temperature low and use a method that minimizes the thermal history, such as UV irradiation or electron beam irradiation. In addition, these functional layers can be provided during the polyester film forming process. This allows the polarizing plate of the present invention to be integrated with the glass plate of the liquid crystal cell without impairing the increased heat shrinkage rate. This is a more desirable embodiment because it makes it possible to Easy-adhesion layer, hard coat layer, anti-glare layer, anti-reflection layer, low-reflection layer, low-reflection layer, anti-reflection The functional layers such as anti-glare layer, low reflection anti-glare layer, anti-static layer, etc. are made of polyester film with polarizers stacked on top of each other. The functional layers are laminated on the opposite side of the laminated surface, and the contraction force F f , F v It is preferable that the above-mentioned conditions are satisfied.

[0039] (Method of manufacturing oriented polyester film) The polyester film used in the present invention is produced by a general method for producing polyester films. For example, the polyester resin may be melted and extruded into a sheet. The molded non-oriented polyester is heated at a temperature above the glass transition temperature, and the speed difference of the rolls is After stretching the film in the machine direction using a tenter, it is stretched in the cross direction using a tenter and then heat-treated (heat-set). The film may be uniaxially stretched or biaxially stretched. is a uniaxially stretched film that is strongly stretched mainly in the transverse direction or a uniaxially stretched film that is strongly stretched mainly in the longitudinal direction. The film is a stretched film, and may be slightly stretched in a direction perpendicular to the main stretching direction. MD is an abbreviation for Machine Direction, and in this specification, It is sometimes called the flow direction, longitudinal direction, or vertical direction. Also, TD stands for Transverse It is an abbreviation for Direction, and may be referred to as width direction or lateral direction in this specification.

[0040] The polyester film has a shrinkage force F f is between 800N / m and 9000N / m In addition, it is preferable to adjust the film thickness, elastic modulus and heat shrinkage rate.

[0041] (Method for adjusting the elastic modulus of polyester film) The elastic modulus of the polyester film used as the polarizer protective film is When the direction of the film is the same as that of the MD during film formation, the elastic modulus of the MD is When the elastic modulus of the stretched polyester film is the same as that of the TD film, The film thickness may be adjusted by a conventionally known method. Specifically, when the direction is the stretching direction, the stretching ratio is set high, and when the direction is perpendicular to the stretching direction, In the case of the stretching direction, the stretching ratio should be set low.

[0042] (Method for adjusting the heat shrinkage rate of polyester film) The heat shrinkage rate of the polyester film used as the polarizer protective film is When the axial direction is the same as the MD direction at the time of polyester film production, the heat shrinkage rate of the MD is If the thermal shrinkage rate of the stretched polyester film is the same as that of the TD, The film may be prepared by a conventional method known in the art.

[0043] To adjust the MD heat shrinkage of polyester film, for example, Distance between the clip holding the film width direction edge and the adjacent clip during the cooling process By expanding the clip, it can be stretched to the MD, or by reducing the clip interval, it can be contracted to the MD. In addition, the film can be adjusted by cooling it after stretching and heat setting. When cutting or separating the film from the clips that grip the widthwise ends, By adjusting the pulling force, the film can be stretched or shrunk in the MD direction. In addition, functional layers can be added in offline processes after film formation. When the temperature is increased for this purpose, the thermal shrinkage rate changes during the heating and cooling process, so the film It can also be adjusted by adjusting the force to stretch or contract in the MD.

[0044] To adjust the TD heat shrinkage rate of polyester film, for example, after stretching and heat setting, During the cooling process, the clips holding the film's widthwise edge are positioned on the opposite side of the film's width. The distance between the clips can be increased to stretch the TD, or reduced to fit the TD. It can be adjusted by contracting it.

[0045] Contraction force F v is the ratio of contractile forces (F f / F v ) is between 1.0 and 12.0. The elastic modulus and thermal conductivity of the polyester film are preferably 2.5 or more and 12.0 or less. It is preferable to adjust the shrinkage rate.

[0046] (Method for adjusting the inclination of the main axis of shrinkage of polyester film) The tilt of the shrinkage axis of the polyester film used as the polarizer protective film is As published in / JP2014 / 073451 (WO2015 / 037527) In the cooling process after stretching and heat treatment of polyester film by tenter or after film formation It can be adjusted in the fly process. Specifically, it can be removed in the cooling process. Shrinkage due to incomplete stretching and thermal stress due to cooling occur, and Depending on the balance between the two, either upstream or downstream pull occurs. In order to reduce the tilt of the shrinkage axis, the filler The shrinkage force in the film flow direction (the sum of the shrinkage force due to stretching and the shrinkage force due to cooling) is uniform. To make it uniform, it is necessary to adjust the temperature so that the shrinkage force is high in the film flow direction. Shrinkage in the film flow direction in the temperature range, or the temperature where the shrinkage force is low in the film flow direction It is desirable to stretch the film in the machine direction in the shrinking or stretching region. In addition, when cutting or separating the film edge, the cutting / separation method can be used. Below this temperature range, the material shrinks freely in the width direction, and the thermal shrinkage rate below this temperature range is small. Therefore, caution is required.

[0047] The polarizing plate is formed by applying the polyester film for protecting a polarizer of the present invention to at least one surface of a polarizer. On the other side of the polarizer, a TAC film, an acrylic film, and It is preferable that a film having no birefringence, such as a norbornene film, is laminated. Alternatively, a thin polarizing plate with no film laminated on the other side of the polarizer can also be used. In this case, the film is laminated on the other surface of the polarizer. However, a coating layer may be laminated on the polarizer. Examples of the coating layer include a hard coat layer. The film may be a functional layer or a retardation film formed by coating. In addition, if a film or coating layer other than the polyester film for protecting a polarizer of the present invention is attached to the polarizer, When laminating, a polyester film for protecting the polarizer in the direction parallel to the transmission axis of the polarizer The shrinkage force of films and coating layers other than the film, and the polarization in the direction parallel to the absorption axis of the polarizer The shrinkage force of films and coating layers other than the polarizer protection polyester film is Polyester film for F f The value of the polarizer protection polyester is preferably equal to or less than this value. Stereo film F v In addition, the value in the direction parallel to the transmission axis of the polarizer is preferably equal to or less than the value of The shrinkage force of films and coating layers other than the polyester film for protecting the polarizer, and the shrinkage force of the polarizer Films and coatings other than polyester films for polarizer protection in the direction parallel to the absorption axis The shrinkage force of the layer is preferably 250 N / m or less, more preferably 200 N / m or less. The shrinkage force of films and coating layers other than the protective polyester film is It can be measured in the same way as in the case of the film or coating layer thickness (mm) × Elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80℃ ÷ 100 × 1000 .

[0048] Industrially, polarizing plates are made up of a long piece of polarizer and a long piece of polyester film for protecting the polarizer. The polarizers are usually laminated in a vertical direction using an adhesive in a roll-to-roll fashion. Since it is produced by stretching in both directions, it has an absorption axis in MD and a transmission axis in TD.

[0049] Therefore, from the viewpoint of industrial production of polarizing plates, the polyester for protecting a polarizer of the present invention The film is preferably one of the following (1) and (2). (1) TD shrinkage force F of polyester film TD is 800N / m or more and 9000N / m or more Below. However, the contractile force F TD (N / m) is the thickness of the polyester film (mm) x the elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) after treatment at 80°C for 30 minutes ÷ 100 × 1000. The elastic modulus and heat shrinkage rate are the TD elastic modulus and TD heat shrinkage rate of polyester film, respectively. be. (2) TD shrinkage force F of polyester film TD and MD shrinkage of polyester film force F MD Ratio of (F TD / F MD ) is preferably 2.5 or more and 12.0 or less. However, the contractile force F MD (N / m) is the thickness of the polyester film (mm) x the elastic modulus ( N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80°C ÷ 100 × 1000. , elastic modulus, and heat shrinkage are the MD elastic modulus and MD heat shrinkage of the polyester film, respectively. is the rate.

[0050] In addition, the polyester film for protecting a polarizer of the present invention is heat-shrinkable. It is preferable that the direction in which the modulus is maximum is approximately parallel to TD. The term "almost parallel" means that the direction in which the heat shrinkage rate of the polyester film is maximum is parallel to the TD direction. The absolute value of the angle (the gradient of the thermal shrinkage rate) is allowed to be 15 degrees or less. The inclination is preferably 12 degrees or less, more preferably 10 degrees or less, and even more preferably Preferably, the angle is 8 degrees or less, more preferably 6 degrees or less, and particularly preferably 4 degrees or less. The lower limit is preferably 2 degrees or less. is 0 degrees. However, the TD shrinkage force F of the polyester film TD and MD convergence of polyester film Contraction force F MD Ratio of (F TD / F MD ) is 2.5 or more and 12.0 or less, polyester fiber Even if the absolute value of the angle between the direction in which the film's thermal shrinkage rate is maximum and the TD is 40 degrees or less, This can reduce warping of the liquid crystal panel. The angle is preferably 35 degrees or less.

[0051] In consideration of industrially manufacturing polarizing plates in a roll-to-roll format as described above, In this case, F TD is F f Since it is equivalent to F TD and a preferred range of F f The preferred ranges of F are the same. TD / F MD is F f / F v It is equivalent to Therefore, the preferred ranges for both are the same. This corresponds to the "elastic modulus of the polyester film in the direction of the transmission axis of the polarizer." Therefore, the preferable ranges for both are the same. The "thermal shrinkage rate of the polyester film in the direction of the transmission axis of the polarizer" is The heat shrinkage rate corresponds to the heat shrinkage rate when heat treated at 80°C for 30 minutes. are identical.

[0052] A liquid crystal display device comprises at least a backlight source and a liquid crystal disposed between two polarizing plates. At least one of the two polarizing plates is made of the polyester for protecting a polarizer of the present invention. The polarizing plate preferably uses a steric film as a polarizer protective film. Alternatively, both of the two polarizing plates may be the polarizing plate of the present invention.

[0053] The polyester film for protecting a polarizer of the present invention is The polarizer on the light source side is measured from the polarizer protective film on the light source side and / or the polarizer on the light source side. It is preferably used in place of a protective film.

[0054] Usually, a liquid crystal display device has a rectangular shape (the two panels used in the liquid crystal display device The polarizing plates are also rectangular), one polarizing plate has its long side parallel to the absorption axis, and the other polarizing plate The long sides of the lenses are parallel to the transmission axes, and the lenses are arranged so that their absorption axes are perpendicular to each other. Generally, a polarizing plate in which the long side and the absorption axis are parallel to each other is used for viewing an image of a liquid crystal display device. The polarizer is used as a viewing-side polarizer, and the long side of the polarizer and the transmission axis are parallel to each other. It is used as a polarizing plate on the light source side of a display device. At least, the long side of the polarizing plate and the transmission axis are parallel. The use of the polarizing plate of the present invention as a polarizing plate having a relation to the polarizing plate suppresses warping of the liquid crystal panel. In addition, a polarizing plate in which the long side and the transmission axis are parallel to each other and The polarizing plate of the present invention can be used for both polarizing plates in which the long side and the absorption axis are parallel to each other. Both are preferable. [Example]

[0055] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the above, and may be implemented by making appropriate modifications within the scope of the present invention. It is also possible to do so, and all of these are included in the technical scope of the present invention.

[0056] (1) Contraction force F f Contraction force F of polyester film f was calculated from the following formula. The thickness, modulus of elasticity, and heat shrinkage of the film are measured values ​​as explained below. This is the elastic modulus of the polyester film in the direction parallel to the transmission axis. is the heat shrinkage rate of the polyester film in the direction parallel to the transmission axis of the polarizer. . Contraction force F f (N / m) = Polyester film thickness (mm) × Elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80℃ ÷ 100 × 1000

[0057] (2) Contraction force F v Contraction force F of polyester film v was calculated from the following formula. The thickness, modulus of elasticity, and heat shrinkage of the film are measured values ​​as explained below. This is the elastic modulus of the polyester film in the direction parallel to the absorption axis. is the heat shrinkage rate of the polyester film in the direction parallel to the absorption axis of the polarizer. . Contraction force F v (N / m) = Polyester film thickness (mm) × Elastic modulus (N / mm 2 ) × Heat shrinkage rate (%) after 30 minutes at 80℃ ÷ 100 × 1000

[0058] (3) Film thickness The thickness of the polyester film (mm) is measured after leaving it for 168 hours in an environment of 25°C and 50% RH. The measurement was carried out using an electric micrometer (Fineruh, Millitron 1245D). , and the units were converted to mm.

[0059] (4) Elastic modulus of polyester film The elastic modulus of polyester film was measured after leaving it for 168 hours in an environment of 25°C and 50% RH. Seiko Instruments' dynamic viscoelasticity measuring instrument was used in accordance with S-K7244 (DMS). The evaluation was carried out using a measuring device (DMS6100). The tension mode was used, the driving frequency was 1 Hz, and the The temperature dependency is 25℃ to 120℃ under the conditions of a chuck distance of 5mm and a temperature rise rate of 2℃ / min. The average of the storage modulus between 30°C and 100°C was taken as the elastic modulus. For the polarizer film, the elastic modulus and polarization of the polyester film in the direction parallel to the polarizer transmission axis were The elastic modulus of the polyester film in the direction parallel to the photon absorption axis was measured. The above measurements were taken on the polyester film alone (polyester film for protecting polarizers alone). ) was performed.

[0060] (5) Heat shrinkage rate and heat shrinkage rate gradient of polyester film After leaving the polyester film in an environment of 25°C and 50% RH for 168 hours, A circle of 1 m was drawn and the diameter of the circle was measured using an image dimension measuring instrument (IM6, manufactured by KEYENCE). 500), the length before treatment was measured every 1°. Next, the gear set at 80°C was Heat treatment was carried out in an oven for 30 minutes, and then the sample was left in an environment set at room temperature (25°C) for 10 minutes. After cooling for 1 minute, the length was evaluated every 1° in the same manner as before the treatment, and the length after the treatment was recorded. The above treatment is performed on the polyester film alone (polyester film for protecting polarizers alone). went.

[0061] The heat shrinkage rate was evaluated for each angle using the following calculation formula. Heat shrinkage rate = (length before treatment - length after treatment) / length before treatment x 100 Thus, for the polyester film, the polyester film in the direction parallel to the polarizer transmission axis The heat shrinkage rate of the film and the heat shrinkage rate of the polyester film in the direction parallel to the polarizer absorption axis were measured. I asked.

[0062] As above, evaluate 360° at 1° intervals to identify the direction with the maximum thermal shrinkage rate, and then The absolute value of the angle between the direction of the polarizer and the transmission axis of the polarizer was taken as the gradient of the heat shrinkage. The tilt is defined as a narrow angle from the transmission axis direction of the polarizer, and is in the range of 0 to 90°.

[0063] (6) Warping of LCD panels The liquid crystal panels produced in each example and comparative example were heated for 30 minutes in a gear oven set at 80°C. After that, the sample was cooled for 30 minutes in an environment set at room temperature (25°C, 50% RH). After that, place the product on a horizontal surface with the convex side facing downwards, measure the height of the four corners with a tape measure, and use the maximum value to determine the amount of warping. The amount of warpage was evaluated as follows. ○: 0mm or more, less than 2.0mm △: 2.0mm or more, 3.0mm or less ×: Over 3.0mm

[0064] (7) Refractive index of polyester film Using a molecular orientation meter (Oji Measuring Instruments, MOA-6004 type molecular orientation meter), The slow axis direction of the film was determined, and the film was then cut into 4 cm pieces so that the slow axis direction was parallel to the long side of the measurement sample. A rectangle measuring 2 cm was cut out and used as a measurement sample. Biaxial refractive index (refractive index in the slow axis direction: Ny), fast axis (refractive index in the direction perpendicular to the slow axis direction: The refractive index in the thickness direction (Nz) and the refractive index in the thickness direction (Nx) were measured using an Abbe refractometer (Atago Co., Ltd., NAR-4 The NZ coefficient was calculated using these values.

[0065] Retardation is the anisotropy of the refractive index of two perpendicular axes on the film (△Nxy = |Nx -Ny|) and the film thickness d (nm) (△Nxy×d) and is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (△Nxy) is The orientation was determined by the following method: The slow axis direction of the film was determined using a molecular orientation meter, and the slow axis direction was aligned with the long side of the measurement sample. A 4cm x 2cm rectangle was cut out so that it was parallel to the surface, and used as a measurement sample. For the sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: Ny, refractive index in the slow axis direction and perpendicular to the slow axis direction: The refractive index in the direction of the sample (Nx) and the refractive index in the thickness direction (Nz) were measured using an Abbe refractometer (Atago Co., Ltd.). The absolute value of the difference in refractive index between the two axes ( The refractive index anisotropy (ΔNxy) was defined as |Nx-Ny|. The film thickness d (nm) was the The measurement was carried out using a micrometer (Finerufu Co., Ltd., Millitron 1245D). The refractive index anisotropy (△Nxy) and the film thickness d (nm) were converted to nm. The retardation (Re) was calculated from Nxy×d.

[0066] (8) Thickness retardation (Rth) The thickness retardation is the difference between the two birefringences △N when viewed from the cross section of the film thickness direction. Let xz (=|Nx-Nz|) and △Nyz (=|Ny-Nz|) be the film thickness d. This is a parameter that indicates the average retardation obtained by multiplying the retardation values. In the same way, Nx, Ny, Nz and film thickness d (nm) are calculated, and (△Nxz × d) The average value of (ΔNyz×d) was calculated to determine the retardation in the thickness direction (Rth).

[0067] (Production Example 1 - Polyester A) The temperature of the esterification reactor was raised to 200°C, and at that point, 86.4 parts by mass of terephthalic acid was added. and 64.6 parts by mass of ethylene glycol were charged, and antimony trioxide was added as a catalyst while stirring. 0.017 parts by mass of magnesium acetate, 0.064 parts by mass of magnesium acetate tetrahydrate, and triethylammonium hydroxide. Then, the mixture was pressurized and heated to a gauge pressure of 0.34 MPa and 24 After the pressurized esterification reaction was carried out at 0°C, the esterification reactor was returned to atmospheric pressure and 0% phosphoric acid was added. 0.014 parts by mass of trimethyl phosphate was added. After 15 minutes, a dispersion treatment was carried out using a high-pressure disperser. Thereafter, the obtained esterification reaction product was transferred to a polycondensation reactor and subjected to polycondensation reaction under reduced pressure at 280°C. The response was as follows.

[0068] After the polycondensation reaction is complete, the mixture is filtered using a Naslon filter with a 95% cutoff diameter of 5 μm. Cooling water extruded in strand form from a nozzle and filtered in advance (pore size: 1 μm or less) The resulting polyethylene terephthalate was cooled and solidified using a tungsten fluoride (TFA) and cut into pellets. The intrinsic viscosity of the resin (A) was 0.62 dL / g, and the inert particles and internal precipitated particles were substantially (Hereafter, abbreviated as PET(A)).

[0069] (Production Example 2 - Polyester B) The dried UV absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzyl) 10 parts by mass of benzoxazinon-4-one), PET (A) containing no particles (intrinsic viscosity 0.62 dl / g) 90 parts by mass were mixed and extruded in a kneading extruder to obtain a polypropylene resin containing an ultraviolet absorber. Ethylene terephthalate resin (B) was obtained (hereinafter referred to as PET (B)).

[0070] (Production Example 3 - Preparation of Adhesion-Modifying Coating Liquid) By carrying out an ester exchange reaction and a polycondensation reaction by a conventional method, a dicarboxylic acid component (dicarboxylic acid (based on the total carboxylic acid component) terephthalic acid 46 mol %, isophthalic acid 46 mol %, and 5- Sodium sulfonatoisophthalate 8 mol%, as glycol component (total glycol component A combination of 50 mol% ethylene glycol and 50 mol% neopentyl glycol (based on the total mass) A water-dispersible sulfonate metal salt group-containing copolymer polyester resin was prepared. 1.4 parts by mass, isopropyl alcohol 38 parts by mass, n-butyl cellosolve 5 parts by mass, After mixing 0.06 parts by mass of anionic surfactant, the mixture is heated and stirred until it reaches 77°C. 5 parts by mass of water-dispersible sulfonic acid metal salt-containing copolymer polyester resin was added to form a resin mass. After stirring until the solids disappeared, the resin water dispersion was cooled to room temperature and the solids concentration was 5.0 A homogeneous water-dispersible copolymer polyester resin solution with a content of 100% by weight was obtained. 3 parts by mass of Sylysia 310 (manufactured by Sylysia Corporation) was dispersed in 50 parts by mass of water, and then 99.46 parts by mass of the water-dispersible copolymer polyester resin solution was mixed with 0.05 parts by mass of a water dispersion of Sylysia 310. 0.54 parts by mass of the hydroxybenzoate was added, and 20 parts by mass of water was added while stirring to obtain an adhesion-modifying coating liquid.

[0071] Example 1 <Production of Polyester Film 1 for Protecting Polarizer> 90 mass of particle-free PET(A) resin pellets as raw material for the intermediate layer of the base film 10 parts by mass of PET(B) resin pellets containing ... After pressure drying (1 Torr), the mixture was fed to extruder 2 (for intermediate layer II) and PET(A ) was dried by a conventional method and fed to extruder 1 (for outer layer I and outer layer III), The two polymers were dissolved at 5°C. Each of them was placed in a stainless steel sintered filter medium (nominal filtration accuracy). The filter is then stacked in a two-type, three-layer merging block, and the filter is then removed from the nozzle. After extruding it into a sheet, it is cast at a surface temperature of 30°C using an electrostatic casting method. The film was then wound around a rolling drum and cooled to solidify, forming an unstretched film. The discharge rates of the extruders were adjusted so that the thickness ratio of the III layer was 10:80:10.

[0072] Next, the unstretched PET film was coated on both sides by the reverse roll method with a dry coating amount of 0.08g / m 2 After applying the adhesiveness modifying coating liquid, the adhesiveness modifying coating liquid was heated at 80°C for 20 seconds. Dry.

[0073] The unstretched film on which this coating layer was formed was introduced into a tenter stretching machine, and the edges of the film were cleaned. While being held by a clamp, the film was introduced into a hot air zone at a temperature of 105°C and stretched 4.0 times in the TD direction. The film was then heat treated at 180°C for 30 seconds, and then cooled to 100°C. The film is stretched 1.0% in the width direction and then cooled to 60°C. Both ends of the film are held. The clips were released and the film was taken off with a tension of 350 N / m, resulting in a uniaxially oriented film with a thickness of approximately 80 μm. A jumbo roll made of PET film was taken and divided into three equal parts. Three slit rolls (L (left side), C (center), R (right side)) were obtained. A polyester film 1 for protecting a polarizer was obtained from Littroll. For film 1, the direction in which the thermal shrinkage rate was greatest was 7.0 degrees from the TD.

[0074] <Creating LCD panels> 1. Polyester film for protecting polarizer on one side of polarizer made of PVA, iodine, and boric acid The polarizer protective polyester film 1 is attached so that its transmission axis is parallel to the TD axis of the polarizer. A TAC film (manufactured by Fujifilm Corporation, thickness 80 mm) was attached to the opposite side of the polarizer. A polarizing plate on the light source side was created by attaching a thin film (film thickness: 1.0 μm).

[0075] A 46-inch IPS LCD TV that uses a 0.4mm thick glass substrate for the liquid crystal cell. I removed the LCD panel from the TV. I peeled off the light source side polarizer from the LCD panel and replaced it with The light source side polarizing plate prepared above was peeled off so that the transmission axis of the polarizer was the same as that of the light source side polarizing plate before peeling off. The PSA is then attached to the liquid crystal cell so that the direction of the film is aligned with the horizontal direction (parallel to the horizontal direction). Nell was created. The polarizer protection polyester film 1 is positioned on the far side (opposite side) of the liquid crystal cell. The light source side polarizing plate was attached to the liquid crystal cell as shown in Fig. 1. The viewing side polarizing plate had a polarizer on both sides. The TAC film is laminated, and the absorption axis of the polarizer is parallel to the horizontal direction. It was attached to the liquid crystal cell like this.

[0076] Example 2 <Production of Polyester Film 2 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 1.5% in the width direction, and the film was the same as polyester film 1 for protecting polarizer. In the same manner, a polyester film 2 for protecting a polarizer was obtained. For Room 2, the direction in which the thermal shrinkage rate was greatest was 6.5 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that Film 2 was used instead.

[0077] Example 3 <Production of Polyester Film 3 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 1.7% in the width direction, and the film was the same as polyester film 1 for protecting polarizer. In the same manner, a polarizer protective film 3 was obtained. The direction in which the reduction ratio was greatest was 5.3 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that Film 3 was used instead.

[0078] Example 4 <Production of Polyester Film 4 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 2.0% in the width direction, and after stretching 4 times in the TD, it was Before the heat treatment for 10 seconds, a hard coat layer coating solution was applied to one side of the polyester film. A polarizer protective film 4 was obtained in the same manner as in the polarizer protective polyester film 1 except for the above. The direction in which the heat shrinkage rate of the polyester film 4 for protecting polarizers is the maximum is 4 mm from the TD. It was 0.8 degrees. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that Film 4 was used instead.

[0079] Example 5 <Production of Polyester Film 5 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 160 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 4, except that The polyester film 5 for protecting a polarizer was prepared by the method in which the heat shrinkage rate was maximized. The direction was 4.8 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that Film 5 was used instead.

[0080] Example 6 <Production of Polyester Film 6 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 1.5% in the machine direction. In the same manner as above, a polyester film 6 for protecting a polarizer was obtained. For Film 6, the direction in which the thermal shrinkage rate was greatest was 9.0 degrees from the MD. <Creating LCD panels> In the preparation of the light source side polarizing plate in Example 1, instead of the polyester film for protecting the polarizer, The polarizer protection polyester film 6 is used to protect the polarizer. The polarizing plate on the light source side was created by pasting Stereo Film 6 so that the MD was parallel. A liquid crystal panel was fabricated in the same manner as in Example 1.

[0081] Example 7 <Production of Polyester Film 7 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 1.7% in the machine direction. In the same manner as above, a polyester film 7 for protecting a polarizer was obtained. For Film 7, the direction in which the thermal shrinkage rate was greatest was 8.3 degrees from the MD. <Creating LCD panels> In Example 6, the polarizer protecting polyester film 6 was replaced with a polarizer protecting polyester film. A liquid crystal panel was produced in the same manner as in Example 6, except that Film 7 was used instead.

[0082] Example 8 <Production of Polyester Film 8 for Protecting Polarizer> In the production of the polyester film 1 for protecting a polarizer in Example 1, the film was cooled to 100°C. The film was stretched by 2.0% in the machine direction. In the same manner as above, a polyester film 8 for protecting a polarizer was obtained. For Film 8, the direction in which the thermal shrinkage rate was greatest was 7.0 degrees from the MD. <Creating LCD panels> In Example 6, the polarizer protecting polyester film 6 was replaced with a polarizer protecting polyester film. A liquid crystal panel was produced in the same manner as in Example 6 except that Film 8 was used instead.

[0083] Example 9 <Production of Polyester Film 9 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 160 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 8, except that The polyester film 9 for protecting a polarizer was obtained by the method in which the heat shrinkage rate was maximized. The direction was 7.0 degrees from the MD. <Creating LCD panels> In Example 6, the polarizer protecting polyester film 6 was replaced with a polarizer protecting polyester film. A liquid crystal panel was produced in the same manner as in Example 6, except that Film 9 was used instead.

[0084] Example 10 <Production of Polyester Film 10 for Protecting Polarizer> The film was stretched 4.0 times in the TD, but was stretched 4.0 times in the MD and 1.0 times in the TD. Polarizer protective film 1 was prepared in the same manner as polarizer protective polyester film 6, except for the above changes. The polyester film 10 for protecting a polarizer had a maximum heat shrinkage rate in the direction of M It was 8.7 degrees from D. <Creating LCD panels> In Example 6, the polarizer protecting polyester film 6 was replaced with a polarizer protecting polyester film. A liquid crystal panel was produced in the same manner as in Example 6, except that Film 10 was used instead.

[0085] Example 11 <Production of Polyester Film 11 for Protecting Polarizer> In the production of the polyester film 10 for protecting a polarizer in Example 10, the temperature was cooled to 100°C. The polyester film for protecting the polarizer was used except that the cooled film was stretched by 1.7% in the machine direction. A polyester film 11 for protecting a polarizer was obtained in the same manner as in Film 10. For STEEL film 11, the direction in which the thermal shrinkage rate was greatest was 7.5 degrees from the MD. <Creating LCD panels> In Example 10, the polyester film 10 for protecting a polarizer was replaced with a polyester film for protecting a polarizer. A liquid crystal panel was fabricated in the same manner as in Example 10, except that the PET film 11 was used instead.

[0086] Example 12 <Production of Polyester Film 12 for Protecting Polarizer> In the production of the polyester film 10 for protecting a polarizer in Example 10, the film was cooled to 100°C. The film was stretched by 5.0% in the width direction. In the same manner as in Example 0, a polyester film 12 for protecting a polarizer was obtained. For film 12, the direction in which the thermal shrinkage rate was maximum was 1.8 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that film 12 was used instead.

[0087] Example 13 <Production of Polyester Film 13 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be set to 60 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 4, except for the above. Film 13 was obtained. The polyester film 13 for protecting a polarizer had the maximum heat shrinkage rate. The direction was 4.8 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that film 13 was used instead.

[0088] Example 14 <Production of Polyester Film 14 for Protecting Polarizer> During the cooling process after stretching 1.7% in the width direction, both ends of the film are held. The polarizer protective film was the same as polarizer protective film 3 except that the clip width was not changed. The polyester film 14 for protecting a polarizer was obtained in the direction in which the heat shrinkage rate was maximum. , 33.0 degrees from TD. <Creating LCD panels> The same as in Example 3 except that the polarizer protective film 1 was replaced with the polarizer protective film 14. We used this to create an LCD panel.

[0089] (Comparative Example 1) <Production of Polyester Film 15 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 200 μm. The width of the clips holding both ends of the film during the cooling process after stretching and heat setting was Polarizer protective film 15 was obtained in the same manner as Polarizer protective film 1, except that the film was passed through without any change. The direction in which the heat shrinkage rate of the polyester film 15 for protecting a polarizer is the maximum is from MD to It was 20.0 degrees. <Creating LCD panels> The polarizer protective film 15 was replaced with the polarizer protective film 15. The polarizing plate on the light source side was created by laminating the protective film so that the MD of the protective film was parallel. A liquid crystal panel was fabricated in the same manner as in Example 1.

[0090] (Comparative Example 2) <Production of Polyester Film 16 for Protecting Polarizer> In the cooling process after stretching and heat setting, the film is not stretched by 1.0% in the width direction. The film was the same as polarizer protective film 1 except that the clips holding both ends of the film were released at 95°C. The polarizer protective film 16 was obtained in the same manner. The polarizer protective polyester film 16 was heat-shrunk. The direction with the highest rate was 1.0 degrees from the MD. <Creating LCD panels> The polarizer protective film 16 was replaced with the polarizer protective film 16, and the transmission axis of the polarizer and the polarization The polarizing plate on the light source side was created by laminating the protective film so that the MD of the protective film was parallel. A liquid crystal panel was fabricated in the same manner as in Example 1.

[0091] (Comparative Example 3) <Production of Polyester Film 17 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be set to 50 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 1, except for the above. Film 17 was obtained. The polyester film 17 for protecting a polarizer had the highest heat shrinkage rate. The direction was 7.0 degrees from the TD. <Creating LCD panels> In Example 1, the polyester film 1 for protecting a polarizer was A liquid crystal panel was produced in the same manner as in Example 1 except that film 17 was used instead.

[0092] Comparative Example 4 <Production of Polyester Film 18 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 160 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 11, except that The polyester film 18 for protecting the polarizer was obtained. The polyester film 18 had the highest heat shrinkage rate. The direction of the axial tilt was 6.5 degrees from the MD. <Creating LCD panels> In Example 11, the polarizer protecting polyester film 11 was replaced with a polarizer protecting polyester film. A liquid crystal panel was fabricated in the same manner as in Example 11 except that the PET film 18 was used instead.

[0093] (Comparative Example 5) <Production of Polyester Film 19 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 160 μm. In the production of the polyester film 1 for protecting a polarizer in Example 1, The film was cooled to 1.0°C and stretched 1.0% in the machine direction. A polyester film 19 for protecting a polarizer was obtained in the same manner as in Film 1. Polyester Film 19 had the maximum heat shrinkage in the direction 11.0 degrees from the MD. . <Creating LCD panels> In the preparation of the light source side polarizing plate in Example 1, instead of the polyester film for protecting the polarizer, The polarizer protection polyester film 19 is used for the polarizer protection. The light source side polarizing plate was created by pasting the TD of Ester Film 19 parallel to the light source side. A liquid crystal panel was produced in the same manner as in Example 1 except for the above.

[0094] (Comparative Example 6) <Production of Polyester Film 20 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be set to 80 μm. The polarizer protective polyester film was prepared in the same manner as the polarizer protective polyester film 19, except for the above. The polyester film 20 for protecting a polarizer was obtained. The polyester film 20 had the maximum heat shrinkage rate. The direction of the movement was 11.0 degrees from the MD. <Creating LCD panels> In Comparative Example 5, the polarizer protective polyester film 19 was replaced with the polarizer protective polyester film 20. A liquid crystal panel was produced in the same manner as in Comparative Example 5, except that the film was replaced with Polyethylene Film 20.

[0095] (Comparative Example 7) <Production of Polyester Film 21 for Protecting Polarizer> A polarizer protective film 21 was obtained in the same manner as the polarizer protective film 20. Polyester Film 21 had the maximum heat shrinkage in the direction 11.0 degrees from the MD. . <Creating LCD panels> In the preparation of the light source side polarizing plate of Example 1, instead of the polyester film 1 for protecting the polarizer, A polyester film 21 for protecting the polarizer is used for the polarizer. The light source side polarizing plate was created by pasting the polyester film 21 so that the MD was parallel. A liquid crystal panel was produced in the same manner as in Example 1 except for the above.

[0096] (Comparative Example 8) <Creating LCD panels> The polarizer protective film 15 is attached so that the transmission axis of the polarizer and the TD of the polarizer protective film are parallel to each other. The liquid crystal panel was prepared in the same manner as in Example 1, except that the light source side polarizing plate was prepared by bonding the polarizing plate as shown in FIG. I created a rule.

[0097] Comparative Example 9 <Production of the Polyester Film 22 for Protecting Polarizer> By adjusting the rotation speed of the casting roll, the film thickness after stretching can be adjusted to 160 μm. In the production of the polyester film 1 for protecting a polarizer in Example 1, The film was cooled to 1.0°C and stretched 1.0% in the machine direction. A polyester film 22 for protecting a polarizer was obtained in the same manner as in Film 1. Polyester film 22 had the maximum heat shrinkage in the direction 11.0 degrees from the MD. . <Creating LCD panels> In the preparation of the light source side polarizing plate of Example 1, instead of the polyester film 1 for protecting the polarizer, A polyester film 22 for protecting the polarizer is used for the polarizer. The light source side polarizing plate was created by pasting the polyester film 22 so that the MD was parallel. A liquid crystal panel was produced in the same manner as in Example 1 except for the above.

[0098] <Production of Polyester Film 23 for Protecting Polarizer> In the production of the polyester film 10 for protecting a polarizer in Example 10, the temperature was cooled to 100°C. The polyester film for protecting the polarizer was used except that the cooled film was stretched by 2.0% in the machine direction. A polyester film 23 for protecting a polarizer was obtained in the same manner as in Film 10. For the steril film 23, the direction in which the thermal shrinkage rate was greatest was 4.5 degrees from the MD. <Creating LCD panels> In Example 10, the polyester film 10 for protecting a polarizer was replaced with a polyester film for protecting a polarizer. A liquid crystal panel was fabricated in the same manner as in Example 10, except that the PET film 23 was used instead.

[0099] [Table 1]

[0100] From the results shown in Table 1, the polarizing plate using the polarizer protective film according to the present invention is It was found that the warping of the panel could be suppressed compared to the polarizing plate of the previous example.

[0101] (Examples 1A to 5A, Example 13A) A polarizing plate having the same configuration as the light source side polarizing plate used in each of Examples 1 to 5 and 13 was used as the light source side polarizing plate. The same as in Examples 1 to 5 and 13 except that the polarizers were both the polarizer on the side of the object and the polarizer on the viewer side. When the results were evaluated separately, the panel's reaction was similar to the results of Examples 1 to 5 and 13 in Table 1 above. In the evaluation, good results (○) were obtained. The light source side polarizer and the viewer side polarizer are positioned on the far side (opposite side) of the liquid crystal cell. The board was pasted onto the board.

[0102] (Examples 1B to 5B, and 13B) In Examples 1A to 5A and 13A, the polarizer protective film on the liquid crystal cell side Examples 1A to 5A and 13A were similar to those in Examples 1A to 5A, except that no TAC film was used. When evaluated separately in the same manner as in Examples 1A to 5A and Example 13A, the performance The flannel showed good results (○) in the warpage evaluation. [Industrial Applicability]

[0103] According to the present invention, a polarizer protective film capable of suppressing warpage of a liquid crystal panel, a polarizing A liquid crystal display device and a display panel can be provided.

Claims

1. A polyester film for protecting a polarizer is laminated on one side of a polarizer, the polyester film being a polyethylene terephthalate film, the polarizer being a polyvinyl alcohol film containing iodine, and the polyester film for protecting a polarizer satisfies the following requirements (1), (2), and (3): (1) The shrinkage force FTD of the polyester film for protecting a polarizer in TD is 800 N / m or more and 9000 N / m or less (wherein the shrinkage force FTD (N / m) is calculated by multiplying the thickness (mm) of the polyester film for protecting a polarizer by the modulus of elasticity (N / mm ２ ) × heat shrinkage rate (%) of treatment at 80°C for 30 minutes ÷ 100 × 1000. Here, the elastic modulus is the elastic modulus of the polyester film for protecting a polarizer in the TD, and the heat shrinkage rate is the heat shrinkage rate of the polyester film for protecting a polarizer in the TD. (2) The ratio (FTD / FMD) of the shrinkage force FTD of the polyester film for protecting a polarizer in the TD to the shrinkage force FMD of the polyester film for protecting a polarizer in the MD is 2.5 or more and 12.0 or less (wherein the shrinkage force FMD (N / m) is the thickness (mm) of the polyester film for protecting a polarizer × the elastic modulus (N / mm ２ ) × heat shrinkage rate (%) of treatment at 80°C for 30 minutes ÷ 100 × 1000. Here, the elastic modulus is the elastic modulus of the polyester film for protecting a polarizer in the MD, and the heat shrinkage rate is the heat shrinkage rate of the polyester film for protecting a polarizer in the MD. (3) The absolute value of the angle between the direction in which the heat shrinkage rate of the polyester film for protecting a polarizer is maximum and the TD is 15 degrees or less.

2. 2. The polyester film for protecting a polarizer according to claim 1, wherein the thickness of the polyester film for protecting a polarizer is 40 to 200 μm.

3. The polyester film for protecting a polarizer according to claim 1, which has a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, or an antireflection and antiglare layer on the surface of the polyester film for protecting a polarizer opposite to the surface on which the polarizer is laminated.

4. A polarizing plate comprising a polarizer and the polyester film for protecting a polarizer according to claim 1 laminated on at least one surface of the polarizer.

5. A polarizing plate comprising a polarizer having the polyester film for protecting a polarizer according to claim 1 laminated on one surface of the polarizer, and no film on the other surface of the polarizer.

6. 6. The polarizer of claim 4 or 5, wherein the polarizer is rectangular in shape, the long sides of the polarizer being parallel to its transmission axis.

7. A liquid crystal display device having a backlight source and a liquid crystal cell disposed between two polarizing plates, at least one of the two polarizing plates being the polarizing plate according to claim 5 or 6.

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